Ceramic coated articles



June 12, 1934. w. .1. sc o-rr 1,962,751

- CERAMIC COATED ARTICLES Filed larch 5, 1932 Patented June 12, 1934 CERAIHIC COATED ARTICLES I Walter J. Scott, Brookfield, Ill., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 5, 1932, Serial No. 597,010

12 Claims.

This invention relates to ceramic coated articles and a method of making the articles.

Objects of the present invention are to provide an article having a protective and durable coating and an effective and eflicient method of making the article.

In apply g an enamel coating to articles, such as number plates for telephone dials, it is frequently convenient to apply the enamel coating only upon the face of the plates because when the entire plate is coated with enamel, difiiculty is often experienced in meeting the close dimensional requirements for seating the plates in the dials. The covering of only the face of the number plate with an enamel coating entails'the necessity of protecting the remainder of the number plate against corrosion. Inaccordance with one embodiment of the invention, an iron or steel base is covered withhigher final temperature of approxin'iatelyv 1310 F. over a period of about 4.4 minutes.

It is believed that a complete understanding of the invention may be had by reference to the .following description taken in conjunction, with 5 the accompanying drawing, in which Fig. 1 .is a side elevation of a numberplate embodying the invention, and

Fig. 2 is a plan view of the number plate shown in Fig. 1. 3

In producing a number plate in accordance with the invention, a circular plate 5 of iron, steel, or other suitable material is made and the upper edges 6 of the plateare slightly rounded. The entire plate is then provided with a black oxide or bower-barfl. coating, by a. process such as disclosed in the patent to Rinck No. 1,690,378, November 6, 1928. The application of the black oxide coating obviates the necessitypf sandblasting or pickling the parts to be coated in a cleanthe enamel is applied directly to a metallic surface. The black oxide coating is impervious to corrosion and, therefore, parts coatedwith black oxide may be stored and subsequently enamelled ing solution immediately prior to the application of the enamel coating as must be done when I period of about two minutes.

black oxide coating tends to cause the enamel to crawl or spread beyond the area upon which 65 it has been dusted. This may be prevented by dipping the plate in a /2 of 1% borax solution, which effectively, prevents the enamel from spreading during the firing operation.

Another method which has been found convenient for applying the enamel to the face of the number plate is to coat the surface of the plate with a tacky substance, such as ceramic ink varnish, a substance well known in the art and readily available on the market. The ink varnish is preferably applied by means of a roller which contacts only with the flat upper face of the number plate and does not apply the tacky substance to the rounded corners. When the ceramic material is dusted on this tacky substance, it adheres thereto and the material dusted on the rounded corners will fall off, thereby forming sharp outlines. along the edges of the enamel. In order to cause the enamel when fused to adhere more firmly to the numberplate, as

material, such as cobalt or nickel nitrate, cobalt or nickel oxide, or other suitable material, may be incorporated in the ink varnish before it isap'plied to the face of the number plate. In some cases it may be desirable to remove the black oxide coating on that portion-of the plate which is to be enamelled to pi omote the adhesion of the enamel to the plate. i

The enamel coating may be applied as a single coating or in some cases it may be desirable to apply several coatings. When several coatings are applied to the number plate, the tacky substance may or may not be applied between the successive layers of enamel. It has been found that when a single coating of enamel is used, it 10 is desirable to use an opacifier in the ink varnish. Suitable opacifiers that may be used are tin oxide, arsenic oxide, or cryolite.

After the enamelling material has'been dusted on the. number plate, the enamel is fired at a temperature of approximately 1575 F. for a This temperature is sufficiently high to fuse the enamel and render it quite fluid. No blistering of the enamel is experienced during this firing operation. Howthe character, background, or ornamental ceramic markings into the enamel, the temperature may not be raised to the firing temperature above mentioned and under these conditions the enamel has a tendency to blister. After the enamel has been formed on the number plate, the enamel is provided with character markings. In some cases a background color is applied to the enamel and characters consisting of numbers and letters are applied to the enamel. The background color is formed by applying a colored enamelling material or a ceramic ink to the enamel surface. been applied, the plate is placed in an oven and baked at a temperature of about 300 F. to"

harden the colored enamel so that it will not become marred in subsequent printing operations. The letters of the number plate are usually in black and are printed on the number plate with a ceramic ink. The plate is then again baked at a temperature of about 300 F. The letters of the number plate are usually colored red and are applied by printing the letters with a ceramic ink of a red color. After the red characters have been applied, the entire plate is again fired. This firing temperature for fusing the characters and background ontothe enamel is carried out at a lower temperature than the firing of the original enamel coating, since otherwise the characters tend to run or spread on the enamel. It has been found that by firing the plates for the background and character fusing operations at a uniform low temperature, there is a tendency. for blisters to' form in the enamel coating. This tendency has been overcome in accordance with the present invention by firing the number plates at an initial temperature of 1160 F. and increasing the temperature to a final temperature of approximately 1310 F. during a period of about 4.4 minutes.

While the invention has'been described in connection with the manufacture of number plates for telephone dials, it will be understood that the invention is equally applicable to enamelling other types of articles and providing character markings thereon. It will be understood, therefore, that the nature and embodiment of the invention described herein is merely illustrative and that many changes and modificationsmay be made therein without departing from the scope and spirit of the invention.

What is claimed is:

l. A ceramic coatedarticle comprising a metallic base, a black iron oxide coating on the base, and an enamel coating on the oxide coat- 2. A method of producing a ceramic coated article which comprises applying a black iron oxide coating to a metallic base, and applying a vitreous enamel coating thereover. a

3. A method of producing a ceramic coated article which comprises applying a black iron oxide coating to a metallic base, applying a tacky substance to the oxide coating, dusting enamelling material on the tacky substance and firing the article to fuse the enamel.

4. A method of producing a ceramic coated article which comprises applying a black iron oxide coating to a metallic base, applying an enamelling material thereover, firing the article to fuse the enamel, applying a character marking on the enamel, and firing the article at a.

After the background color has lower temperature than the firing temperature for the enamel coating to fuse the characters into the enamel.

5. A method of producing a ceramic coated article which comprises applying a black oxide coating to a metallic base, applying an enamelling material over the oxide coating, firing the article at a temperature in the vicinity of 1575 F. for approximately two minutes, applying a character marking to the enamel, and firing the 'article at an initial temperature of approximately 1160-R, increasing to a temperature of approximately 1310 F. for approximately 4.4 minutes.

r 6. A method of producing a ceramic coated article which comprises applying enamelling material to the article, firing the article at a temperature of approximately 1575 F., applying a character marking to the enamel, firing the article at an initial temperature of approximately 1160 F., and gradually increasing the temperature to approximately 1310 F. to fuse the character into the. enamel.

7. A method of producing a ceramic coated article which comprises applying enamelling material to the article, firing the article at a temperature of approximately 1575 F., applying a character marking, baking the article without fusing the enamel, applying a second character marking, firing the article at an initial temperature of approximately 1160 F., and increasing the temperature to approximately 1310 F.

8. A method of producing a ceramic coated article which comprises applying enamelling material to the article, firing the article at a temperature of approximately 1575 F., for about two minutes, applying a character marking to theenamel, firing the article at an initial temperature of approximately 1160 F. and gradually increasing the temperature to approximately 1310 F. during a period of about four minutes.

9. A method of producing a ceramic coated article which comprises applying a black iron oxide coating to an article, applying a ceramic ink varnish to the portion of the article to be enamelled, applying enamelling material over said varnish, and firing the article to fuse the enamel.

10. A method of producing a ceramic coated article which comprises applying a black oxide coating to the article, applyinga borax solution to the oxide coating, placing enamelling material over the portion of the article to be enamelled, and firing the article to fuse the enamel onto, the article.

11. A method of producing a ceramic coated article which comprises applying a black iron oxide coating on the article, applying a tacky substance containing a bonding material to the oxide coating, placing enamelling material on the portion of the article to be enamelled, and firing the enamel to fuse it onto the article.

12. A method of producing a ceramic coated article with multiple enamel coatings, which comprises applying enamelling material to an iron base article, firing the article to fuse said material, applying another quantity of enamelling material over the first coating, and again firing the article at a gradually increasing temperature, the final temperature of the second firing operation being lower than the temperature of the first firing operation.

WALTER J. SCOTT. 

